[core] Fix clang-analyzer-optin.cplusplus.VirtualCall

Detected by clang-tidy-8.

1 files changed, 6 insertions, 4 deletions

diff --git a/src/mbgl/style/expression/expression.cpp b/src/mbgl/style/expression/expression.cpp
index 270fa5eba0..28004bb3e2 100644
--- a/src/mbgl/style/expression/expression.cpp
+++ b/src/mbgl/style/expression/expression.cpp
@@ -16,14 +16,13 @@ public:
     GeoJSONFeature(const Feature& feature_, const CanonicalTileID& canonical) : feature(feature_) {
         geometry = convertGeometry(feature.geometry, canonical);
         // https://github.com/mapbox/geojson-vt-cpp/issues/44
-        if (getType() == FeatureType::Polygon) {
+        if (getTypeImpl() == FeatureType::Polygon) {
             geometry = fixupPolygons(*geometry);
         }
     }
 
-    FeatureType getType() const override  {
-        return apply_visitor(ToFeatureType(), feature.geometry);
-    }
+    FeatureType getType() const override { return getTypeImpl(); }
+
     const PropertyMap& getProperties() const override { return feature.properties; }
     FeatureIdentifier getID() const override { return feature.id; }
     optional<mbgl::Value> getValue(const std::string& key) const override {
@@ -38,6 +37,9 @@ public:
         geometry = GeometryCollection();
         return *geometry;
     }
+
+private:
+    FeatureType getTypeImpl() const { return apply_visitor(ToFeatureType(), feature.geometry); }
 };
 
 EvaluationResult Expression::evaluate(optional<float> zoom,